Fiber tester



April 19, 1955 K. L.I.Y.H.ERTEL 2,706,403

FIBER TESTER Filed Nov. 20, 1953 s Sheets-Sheet 1 INVENTOR K ENNETH L. H ERTEL BY 9 A WoRNEYs April 19, 1955 HERTEL 2,706,403

FIBER TESTER Filed Nov. 20, 1953 SSheets-Sheet 2 INVENTOR KENNETH L. HERTEL BY &

gflll/LTM ATTORNEYS K. L. HERTEL Apr-i1 19, 1955 FIBER TESTER Filed Nov. 20, 1955 3 Sheets-Sheet 3 '[NVENTOR KENNETH L. HERTEL ATTORNEYS United States Patent FIBER TESTER Kenneth L. Hertel, Knoxville, Tenn., assignor to the United States of America as represented by the Secretary of Agriculture Application November 20, 1953, Serial No. 393,530

3 Claims. (Cl. 7389) A non-exclusive, irrevocable, royalty free license in the invention herein described, for all governmental purposes, throughout the world, with the power to grant sublicenses for such purposes, is hereby granted to the Government of the United States of America.

This invention relates to an apparatus for testing samples of fibers such as cotton fibers or other materials having similar properties of strength and elongation. More particularly the invention provides an apparatus for testing flat bundles of cotton fibers to determine both the strength per unit weight and the amount by which the fibers are elongated at break (i. e., the amount by which fibers of known length are stretched at the time they break).

The strength of a bundle of fibers from unprocessed cotton is useful in predicting strength and performance of the finished product. Such tests are made by buyers, by mills in selecting cotton for specific uses, and by breeders in determining the properties of new strains.

Prior to this invention, the Pressley method and apparatus were almost exclusively employed in conducting routine determinations of fiber bundle strength. In accordance with the Pressley method, bundles of fibers are paralleled by combing and the parallel fibers are placed by hand across the clamping areas of a pair of Pressley fiat bundle clamps. The loaded clamps are placed in a Pressley fiber tester, an apparatus which subjects the loaded clamps to a separating force and indicates the amount of force required to separate the clamps by breaking the fibers. The fibers held in the clamps are then removed and weighed and the bundle strength per unit of weight is obtained by dividing the force required to break the fibers by the weight of the fibers.

Pressley flat bundle clamps have resilient rectangular clamping surfaces (a metal surface presses against a metal surface covered with a resilient material). The clamps are loaded with fibers by placing the fibers across the clamping areas of two clamps butted against each other. The clamping surfaces are pressed together under a reproducible pressure by setting up pressure applying bolts with a uniform torque. The portions of fibers which extend beyond the outer edges of the clamping surfaces are trimmed off, so that a known length of fibers are subjected to the test.

An object of the present invention is to provide apparatus for measuring fiber bundle strength, by determining the force required to break bundles of fibers, which avoids disadvantages of the presently used methods and apparatus. Another object is to provide a method and apparatus for measuring both the elongation at break and the breaking strength of a bundle of fibers. Another object is to provide such a method and apparatus in which conventional fiat bundle clamps such as the Pressley fiat bundle clamps can suitably be used.

In general, the embodiment of the strength and elongation tester particularly adapted for testing flat bundles of fibers comprises a flat bundle fiber clamp loading apparatus in which the clamps are loaded with a bundle of fibers which are held under a substantially uniform and reproducible tension while they are in moisture equilibrium with the room; and a strength and elongation tester in which the breaking force is applied at a uniform rate by means of a gravity actuated pendulum, and the amount of tension applied is indicated by the position of a member which stops motion when the fibers break.

Figure l is an illustration of one embodiment of the s tfriength and elongation tester as viewed from the left si e.

Figure 2 is an illustration of the same embodiment as viewed from the front with parts removed.

Figure 3 is an illustration of a fiat bundle fiber clamp loading apparatus.

The frame of the strength and elongation measuring apparatus comprises substantially rectangular base plate 1 and longitudinal upright member 2.

Adjacent to longitudinal member 2 upwardly extend ing pendulum carrier 3 is mounted on offset axle 4 which is rotatably supported by bearing 5. Axle 4 is perpendicular to longitudinal member 2 and is offset to one side of the center of gravity of the carrier 3 so that the action of gravity is capable of rotating axle 4, the pendulum carrier, and its component parts in a clockwise manner.

In the upper portion of carrier 3, pins 6, which are rotatably mounted in bearings 7, support a pendulum comprising pendulum arm 8 and pendulum bob 20. The axis of swinging of the pendulum is parallel to axle 4 and the center of gravity of the pendulum lies on a vertical line which is substantially coincident with the center of axle 4. Arm 8 of the pendulum extends above pins 6 and is slotted to receive and removably hold a fiat bundle fiber clamp.

An adjacent upper portion of carrier 3 is slotted to receive clamp carrying block 10. Block 10 is slotted to receive and removably hold a flat bundle fiber clamp. The action of adjusting bolt 11 moves block 10 back and forth in the slot containing it, and the action of lock bolt 12 holds block 10 in fixed position with respect to carrier 3. By setting block 10 in the proper position, the apparatus can be adjusted to measure the tensile strength and elongation of bundles of fibers of varying lengths.

The length of the bundle of fibers to be measured can suitably be varied by inserting a shim between a pair of fiat bundle clamps and loading the clamps while they are butted against the sides of the shim. When the clamps are loaded in this manner, the length of the bundle of fibers subjected to the test is equal to the distance between the inner edges of the clamping surfaces of the cllamps (when butted together) plus the width of the s 1m.

Carrier 3 is releasably restrained in an upright positlon by latching means 13. The rotation of carrier 3 is damped into a relatively even rate by the action of pneumatic damper 14 connected to axle 4. The rate of rotation is adjustable by means of air intake regulating bolt 15 on damper 14.

The connection of damper 14 to axle 4 is preferably adjusted so that damper 14 begins to provide increasing resistance to the tendency of the rate of rotation of axle 4 to accelerate the instant the center of gravity of carrier 3 descends from its greatest vertical displacement above axle 4, and continues to provide increasing resistance throughout the whole of the arc through which the fibers being tested remain unbroken. This tends to provide a uniform rate of loading of the fibers and to prevent the tester from indicating that a tension greater than that which is actually necessary is being applied at the time the fibers break.

The amount of force applied to the fibers being tested is indicated by the upper end of indicator arm 16 as it moves along scale 17. Scale 17 is attached to frame member 2. Indicator arm 16 is rotatably mounted on sleeve 18, which surrounds and is concentric with axle 4, by means of a bearing providing sufiicient friction to cause arm 16 to remain in any position to which it is moved. Sleeve 18 does not rotate.

Indicator arm 16 is moved by pin 19 attached to pendulum bob 20. Pin 19 engages face 21 of the notch in the lower portion of arm 16.

When loaded fiber clamps are in place in the respective slots in pendulum arm 8 and clamp carrying block 10, and the pendulum carrier 3 is allowed to rotate clockwise due to the action of gravity (i. e., to fall), the fibers, as long as they remain unbroken, prevent the pendulum from swinging far enough for pendulum bob 20 to come to rest against the side of the pendulum carrier. When the pendulum carrier falls with the pendulum, thus restrained from swinging, bob 20 is carried through an arc of a circle which is concentric with axle 4.

Face 21 of the notch in arm 16 is shaped so that pin 19 rotates the arm fast enough to maintain a constant angle with the pendulum, as long as the swinging of the pendulum is restrained by the fibers being tested. When the pendulum is allowed to swing so that bob 20 rests against the side of the pendulum carrier, the swinging causes pin 19 to swing free of face 21. The fall of the carrier with the pendulum bob resting against the side of the carrier moves pin 19 through an are which lies beyond the edge of face 21. Thus, as a sample of fibers is being tested, pin 19 moves clockwise and, by pushing against face 21, moves arm 16 clockwise as more and more tension is applied to the fibers. When the fibers break, pin 19 moves counterclockwise, away from face 21, and also moves further away from axle 4. Then, as the pendulum carrier continues to fall, pin 19 moves clockwise through an arc in which it does not come into 0011- tact with face 21.

Face 22 of the notch in arm 16 extends further from axle 4 and is shaped so that as the pendulum carrier is returned to the vertical position, pin 19 engages face 22 and rotates arm 16 counterclockwise to beyond the zero position of scale 17. The arm is returned to beyond the zero position so that as a sample of fibers is being tested, the arm approaches the zero position from the left while it is moved by the action of pin 19 thrusting against face 21.

Scale 17 is calibrated to indicate in kilograms the amount of force applied to the bundle of fibers.

Scale-carrying arm 23 is rotatably mounted on sleeve 18 by means of a bearing providing sutficient friction to cause the arm to remain in any position to which it is moved. Arm 23 is moved by the action of pin 19 thrusting against face 24 of the notch in the end of the arm. Face 24 is shaped so that when the pendulum carrier falls, if the pendulum is restrained from swinging, pin 19 moves arm 23 through the same are through which arm 16 is moved, but, if the pendulum undergoes some rotation, due to the elongation of the sample being tested, arm 23 lags behind arm 16 by an amount exactly proportional to the amount of elongation. When the pendulum carrier is returned to the vertical position, pin 19 engages face 25 and returns arm 23 beyond the zero position.

Free swinging rider 26 is rotatably mounted on arm 16. Rider 26 has sufiicient weight below its point of support to be held in the vertical position by the action of gravity. The top of rider 26 points to the scale which is carried by arm 23.

The scale carried by arm 23 is calibrated to indicate in millimeters the amount by which the sample being tested increases in length before it breaks. Rider 26 is preferably calibrated to compensate for the bending of pendulum arm 8 as the angle of rotation of the pendulum carrier increases.

Excessive swinging of the pendulum, away from the side of the pendulum carrier, is prevented by adjustable pendulum stop 27.

In the fiat bundle clamp loading apparatus, illustrated in Fig. 3, frame 28 is provided with lock bolt 29, as a means for attaching the apparatus in a fixed position. Vise 30 is mounted on the frame. The vise is provided with jaw opening 31 which has the form of a rectangular cup tilted on its side. The jaw opening is adapted to receive and hold together the lower portions of a pair of flat bundle fiber clamps, such as clamps 9 and 9a. The upper surface of vise 30 is notched to provide groove 32 which is parallel to and adjacent to the upper edge of jaw opening 31. The upper surface of vise 30 is provided with a pair of projections 33, which projections lie between groove 32 and opening 31. The projections are spaced apart the width of the clamping surface of pinch clamp 37. This clamping surface is substantially equal to the width of the clamping surfaces 34 and 34a of flat bundle fiber clamps 9 and 9a, respectively. Projections 33 are arranged to lie in line with the ends of clamping surfaces 34 and 34a when the flat bundle clamps are held in the vise. Retainer 35 is mounted on the surface of vise 30 and arranged to releasably press against the bottom of groove 32 by means of spring 43. Flat projection 36 is arranged to extend the upper surface of vise 30 in a plane parallel to the plane containing the clamping surfaces of the fiat bundle clamps when the clamps are in the vise.

Removable pinch clamp 37 clamps a bundle of fibers 38, and, when the fibers are restrained by the action of retaining member 35, clamp 37 places the fibers under a reproducible tension due to its tendency to slide down projection 36.

A means of pressing clamping surfaces 34 and 34a with a reproducible pressure is provided by the clamp loading apparatus. Vise 30 is rotatably mounted on axle 39 to which is attached spring 40 arranged to resist clockwise rotation of the vise. As clamping bolts 41 and 41a of clamps 9 and 9a are tightened, the amount of torque applied, and therefore the amount of pressure applied to the clamping surfaces, is indicated by the are through which vise 30 is rotated around scale 42. Scale 42 is attached to frame 28.

In testing cotton samples, the samples are preferably allowed to reach equilibrium with the conditions of temperature and humidity of the room. Tufts of fibers are distributed on the teeth of a Fibrograph comb with as little contact by hand as possible.

The fibers on the comb are paralleled in the conventional manner and a flat bundle of fibers is pinched between the jaws of pinch clamp 37 and removed from the fibrograph comb.

Flat bundle clamps 9 and 9a with their jaws open are inserted in the jaws of vise 30 and pressed together. Clamp 37 is placed close to groove 32 and the fibers contained in the clamp are pressed against the bottom of the groove by retainer 35. The fibers are then drawn down across the clamping surfaces 34 and 34a of the fiat bundle clamps. Projections 33 on the vise surface guide the fibers being drawn along and confine them to the width of the clamping surfaces, so that substantially all of the fibers held by one clamp of the pair of fiat bundle fiber clamps extend in parallel lines to be held by the other. Clamp 37 is placed on the projecting surface 36 so that the tendency of the clamp to slide downward places the fibers under a reproducible tension. The fiat bundle clamps are closed and a uniform pressure is applied by means of clamping bolts 41 and 41a in conjunction with the torque indicator scale 42. The portions of fibers extending beyond the clamps are trimmed off flush with outer edges of the flat bundle clamps.

After clamps 9 and 9a are loaded with a bundle of fibers, the pendulum carrier 3 of the strength and elongation measuring apparatus is latched into an upright position. The clamps are then inserted into the slot at the top of pendulum 8 and into carrying block 10 at the top of carrier 3. If spacer shims are used between the fiat bundle clamps, clamp carrying block 10 is adjusted and locked into a position in which no elongation is shown as carrier 3 is rotated while the pendulum is restrained from swinging. The rate at which pendulum carrier 3 will fall is adjusted by means of air intake adjustment bolt 15.

When pendulum carrier 3 is released, it rotates clockwise about axle 4 due to gravity. As long as the fibers held by clamps 9 and 9a remain intact, pendulum 8 moves with the carrier, and is supported thereby only at pivot axis 67. However, the tension applied to the fibers due to the weight of the pendulum causes them to break, at which time the pendulum swings counterclockwise about axis 6-7 until pendulum bob 20 comes to rest against the lower portion of the body of the carrier. The pressure applied at the time the fibers break is indicated by the mark, on scale 17, at which indicator arm 16 stops. The amount of elongation at break is indicated by the mark, on scale 23, at which rider 26 stops.

The weight of the sample tested is obtained by removing and weighing the fibers held by the clamps. This weight is divided into the weight applied at break to obtain the strength per unit weight of the bundle of fibers. This value, multiplied by the length of fiber bundle after trimming, gives a value of tenacity, in terms of breaking load per unit of linear density of the bundle of fibers.

I claim:

1. A strength and elongation measuring apparatus comprising: a frame having a substantially rectangular base plate and a longitudinal upright portion; a rigid upwardly extending pendulum carrier rotatably mounted on an offset axle which is adjacent and perpendicular to said longitudinal portion of the frame and offset enough to allow the action of gravity to rotate the pendulum carrier and its component parts; a pendulum rotatably mounted in the upper portion of the pendulum carrier on an axis of support parallel to the axle of the carrier, with the arm of the pendulum extending above said axis of support, and with the center of gravity of the pendulum lying substantially on a vertical line coincident with the center of the axle of the pendulum carrier; means of removably atfixing a pair of sample holding clamps in, respectively, the said upwardly extending portion of the pendulum arm and the upper portion of the pendulum carrier to hold the sample between the respective members so that the pendulum is restrained from swinging by the sample; a means of damping the rate at which the pendulum carrier is rotated by the action of gravity; a rigid indicator arm rotatably mounted on a sleeve concentric with said axle of the pendulum carrier with an indicator portion extending above the sleeve and a driving portion extending below the sleeve; a rigid scale carrying arm rotatably mounted adjacent to said indicating arm, on said sleeve with a scale carrying portion extending above the sleeve and a driving portion extending below the sleeve; a driving pin attached to the bob of the pendulum and extending into contact with said driving portions of the indicator arm and the scale carrying arm, the end of said driving portion of the indicator arm being provided with a driving pin receiving notch having one side surface shaped to co-act with said driving pin to move the arm through an arc in which it maintains a constant angle with the pendulum and the other side surface shaped to co-act to move the indicator arm beyond the zero position as the pendulum carrier is returned to the vertical position, and the end of the driving portion of the scale carrying arm being also provided with a driving pin receiving notch' having one side surface shaped to co-act with said driving pin to move the arm through an are smaller than the are through which said indicator arm rotates by an amount proportional to the amount by which the sample being tested is elongated, and the other side surface shaped to co-act to move the scale carrying arm beyond the zero position as the pendulum carrier is returned to the vertical position; a gravity actuated free swinging rider mounted on the indicating portion of the indicator arm with its upper end adjacent to the scale carried by the scale carrying arm; and a scale mounted on the longitudinal portion of the frame to extend through an are along which positions are indicated by the upper end of the indicating arm.

2. A flat bundle clamp loading apparatus comprising a frame provided with a means for attachment into a fixed position, a vise rotatably mounted on one portion of said frame, said vise having a jaw opening, in the form of a rectangular cup tilted to one side, adapted to receive and press together the lower portions of a pair of open fiat bundle clamps, the vise being provided in its upper surface with a groove adjacent to and parallel to the upper edge of said jaw opening; a pair of projections on the upper surface of the vise, between said groove and said opening, spaced apart about the length of the clamping surfaces of the fiat bundle clamps and arranged to be in line with the edges of said surfaces when the pair of clamps are held in the vise; a spring loaded member mounted on the upper surface of the vise and arranged to releasably press against the bottom of said groove, the vise being further provided with a flat surface extending in a plane parallel to the plane containing the clamping surfaces of the flat bundle clamps when the clamps are held in the vise, said flat surface being adapted to support a removable pinch clamp; and a removable pinch clamp having a jaw width about equal to the length of the clamping surface of the fiat bundle clamps adapted to lie on said extended flat surface of the vise.

3. A strength and elongation tester comprising: a frame; an upwardly extending pendulum carrier rotatably mounted on the frame on an offset axle around which the pendulum carrier and its component parts rotate due to the action of gravity; a pendulum swingably mounted on the pendulum carrier with the pendulum bob below the mounting and the pendulum arm extending above the mounting; means for clamping a sample between the upwardly extending portion of the pendulum arm and the pendulum carrier, so that the sample restrains the swinging of the pendulum; a tension indicating arm and an elongation indicating arm rotatably mounted on the frame on an axle coincident with the axle of the pendulum carrier; and an indicating arm driving means mounted on the bob of the pendulum in a position in which said driving means contacts and drives the indicating arms in the direction in which the pendulum carrier rotates as long as the sample is intact, and disengages from contact with the indicating arms the instant the sample breaks.

References Cited in the file of this patent UNITED STATES PATENTS 184,830 Brown Nov. 28, 1876 

